I believe it's called masking and can actually get you blacklisted by Google.
phpBB allows you to specify different permissions to spiders and I was utilising this function so the content would be indexed.
It was Kier who mentioned it to me so now I make the same content blocked/available to all guests.
I think some dishonest site owners could do the opposite, and serve up a page loaded with keyword "spamming" in order to boost their page ranking. That's really the type of abuse Google is after. I could have a page with one short paragraph containing the true content, but serve up four additional paragraphs of nonsense to feed the search engines.
The problem with my situation is on a blog where I list recent CD titles in the sidebar. Let's also say that one of these entries was also the spotlight in a blog post (a review, perhaps). In a Google Custom Search, I could search for that particular title, and it would appear as though it were mentioned on dozens of pages (as the sidebar appears on all pages, as well as the home page), where it only really appears as true "content" on the single blog post. I was using the PHP to block that small section of content not only so my own search would work better, but to keep it from diluting the value of search throughout the site. The only change I've noticed is that my "diluted" listings have been mostly trimmed away, and the site is being indexed to my satisfaction. Dishonest? Well...not in my eyes, but if you look at it in technical terms, I
am violating Google's terms of service.
Come to think of it, I may almost be guilty of doing this for the big board vB forum I administrate. Although, I do this using robots.txt, not custom coding. I disallow traffic to the "human" view of the forum, but direct it to the "archive" version instead. I did this mainly to cut down on resource usage. And even after 3-4 years, the site is still ranked on Google where it has always been. In technical terms though, I am not really modifying the content of the site--I am just disallowing traffic to one portion of the site, so attention is focused on another.
